1. Field of Invention
This invention relates to a system for locating a break in a single conductor wire. More particularly, this invention relates to a system for locating a break in a buried single conductor wire such as used with conventional electronic pet confinement systems.
2. Description of the Related Art
Numerous wire bounded pet containment systems have been installed in the United States. The wire defines the perimeter of the area in which the pet is to be confined. A transmitter generates a low strength radio frequency signal which is carried by the wire. A receiver worn by the pet to be confined is tuned to the frequency of the signal carried by wire. Should the pet stray too close to the boundary, a correction signal is generated.
The wire will typically provide many years of service; however, it is subject to potential breakage. Generally, the wire is an 18 gauge, insulated, unshielded, stranded wire. For most installations, the wire is buried between two (2) and six (6) inches underground. The length of the wire may vary between less than 100 yards for a small enclosure and more than 1000 yards for a large enclosure. Accordingly, considerable time and expense is invested in burying the wire and landscaping over the buried wire. Should the wire suffer a break, finding the location of the break is nearly impossible without digging up the entire wire. Further, unnecessary digging to visually inspect the wire increases the risk of additional damage to the wire.
Various devices have been developed for locating breaks in underground wires. Often an ohmmeter which measures the resistance of a wire is used. However, variations in the depth at which the wire is buried lead to fluctuations in the measured resistance. In the case of the pet confinement system, the wire depth can vary without adversely affecting the performance of the pet confinement function rendering the ohmmeter ineffective in locating a break in the buried wire.
Another device used to locate problems with underground wires is a time domain reflectometer (TDR). The TDR looks at the impedance of a wire pair, such as a twisted wire pair or coaxial cable. However, where the impedance of the wire is not constant, the reading of the TDR is ambiguous. Further, the TDR is typically too expensive for the average consumer, thus limiting its use to utility and telephone companies. Accordingly, the TDR is not a viable option for detecting breaks in a single conductor wire used to bound a pet confinement area.
Yet another technique utilizes a radio frequency (RF) signal transmitted through the wire. By monitoring the radio frequency signal, it is possible to determine the approximate location of wire buried underground. However, because the wire acts as an antenna in this technique, the propagation of the RF signal does not allow a determination of a reasonably close approximation of the location of the break in the wire.
Therefore, it is an object of the present invention to provide a system for locating breaks in continuity in a wire, especially those buried underground.
It is another object of the present invention to provide a system which is inexpensive and simple for use in residential applications.
It is a further object of the present invention to provide a system for locating breaks in an unshielded single conductor wire.
It is yet another object of the present invention to provide a method for locating breaks in continuity in a wire.